The present invention relates to data storage using magnetic tape channels, and more particularly, to reading data using an adaptive soft-output detector in the magnetic tape read channels.
A conventional data flow 200 for reading data from a magnetic tape is shown in FIG. 2, according to the prior art. The tape channel 202 receives data that has passed through an error correction code (ECC) encoder and a modulation code (MC) encoder prior to being stored to magnetic tape. Then, the tape channel 202 reads the data as signal xk, to which noise nk is injected yielding a signal yk that is read by the hard detector 204. This detection utilizes a hard detector 204, which does not incorporate soft information in its detecting scheme.
Soft information may be considered a probability that a detected bit (0 or 1) is actually a 0 or a 1. There are different measures of probability that may be implemented in a data flow, but any data flow which uses probabilities (soft information) for decoding must rely on soft detection. However, soft detection in magnetic tape recording channels have typically suffered from some problems. Two types of soft detection typically used are BCJR, which is named after its inventors, Bahl, Cocke, Jelinek, and Raviv, and Dual-Max, which is a derivative (simplified version) of BCJR that relies on an assumption.
However, each of these algorithms experience issues when implemented in data flows for magnetic tape recording channels. Accordingly, it would be beneficial to have a soft detector that is capable of operating in magnetic tape recording channel data flow that alleviates the issues associated with known algorithms.